Study of diffusion and quality control for CoSi2 formation by oxide-mediated cobalt silicidation with Ti capping

Abstract

The mechanism for the enhancement Of COSi2 thin film formation and film quality control by oxide-mediated cobalt silicidation with a Ti-capping layer is discussed. It is found that Ti absorbs oxygen from the SiOx layer, which induces weak points in the SiOx layer and then enhances Co diffusion as well as COSi2 formation. The control of the reactions between Ti and SiOx is significant because a low reaction rate cannot form a suitable thickness Of CoSi2 film, whereas a high reaction rate tends to form the highly resistive CoSi phase. In addition, to maintain the SiOx layer still existing after annealing is also important because if no SiOx layer remains, unreacted Co would react with Si directly to form the highly resistive phase of CoSi, leading to the smooth interface between CoSi2 and Si and dense bulk CoSi2 thin film being destroyed. (c) 2005 American Vacuum Society.